Method for preparing multiple antigen glycopeptide carbohydrate conjugates

ABSTRACT

The present invention relates to a method for preparing carbohydrate T cell epitope conjugates of formula (I): M(T-B) n (I) wherein M, T, B and n are as defined in claim  1.

The present invention relates to a method for preparing carbohydrate Tcell epitope conjugates of formula (I), and to carbohydrate T cellepitope intermediates of formula (II) useful according to said method.

During the last decade, the MAG-Tn3, a new type of synthetic immunogenwhich displays the tumor-associated Tn antigen, has been developed. TheMAG-Tn3 is a fully synthetic glycopeptide (MW=10′897Da) which associatesthe carbohydrate Tn antigen (as a tri-Tn cluster) to a peptidic CD4⁺ Tcell epitope on a tetravalent backbone[5, 9].

MAG-Tn3 corresponds to the following structure[S(α-D-GalNAc)-T(α-D-GalNAc)-T(α-D-GalNAc)-QY⁵IKANS¹⁰°KFIGI¹⁵TEL]₄-K₂-K-β-Ala:

MAG refers to Multiple Antigen Glycopeptide.

Thus, MAG-Tn3 corresponds to a carbohydrate peptide conjugate B4-T4-M ofthe following formula:

Wherein

-   -   KKK is the dendritic polyLysine core (M),    -   T is the peptidic CD4⁺ T cell epitope having the following        sequence: QYIKANSKFIGITEL    -   Tn3 is the tri-Tn B cell epitope having the following sequence:        (α-GalNAc)Ser-(α-GalNAc)Thr-(α-GalNAc)Thr.

Based on successful in vivo results obtained in mice and primates [8,9], the MAG-Tn3 is a good therapeutic vaccine candidate to treatcarcinomas that should advance into a phase I/II clinical trial.

A synthetic route for preparing peptide carbohydrate conjugates, such asnotably MAG-Tn3 has been disclosed in the International PatentApplication WO 98/43677 and in the U.S. Pat. No. 6,676,946. In thisprocess, implemented in small-scale (1-10 mg of final compound), thecarbohydrate Tn3 antigen is incorporated to the dendrimeric peptideM(T)₄ building block. It is to be noted that the incorporation of theTn3 antigen is achieved with the fully unprotected sugar, which mayappear as advantageous since it avoids a final deprotection step.

However, the inventors have shown that such a method fails whenscaled-up. Indeed, the extra-incorporation of Tn residues is difficultto control and affects the crude purity and the overall yield. Further,the purification of such high molecular weight glycopeptide is complex.

Thus, there is a need for an improved method for preparing MAG-Tn3 whichovercomes the drawbacks of the prior art, in particular allows to obtainbetter yields and purity, notably at a larger scale and in a repeatablemanner.

Thus, the present invention, in one aspect, provides a novel process forpreparing MAG-Tn3, and more generally carbohydrate T cell epitopeconjugates of formula (I) (M(T-B)), allowing a large-scale production,with better yields and purity:

nB_(Pr)+M(T)_(n)→M(T-B_(Pr))_(n),  (II)

→M(T-B)_(n),  (I)

The method according to the invention advantageously enables to minimizethe synthesis side-products, to improve the robustness of the process,and to scale-up the synthesis in a repeatable manner.

More specifically, it has been discovered that protecting the hydroxylgroups of the carbohydrate B cell epitope with a suitable protectinggroup (Pr), before incorporating the B cell epitope to the M(T)_(n)building block, enables a better control of the B cell epitopeincorporation, and thus to improve both the yields and purity, inparticular at a large scale.

Another object of the present invention is to provide novel carbohydrateT cell epitope conjugates of formula (II) (M(T-B_(PR))_(n)), whichcompounds are useful for the preparation of carbohydrate T cell epitopeconjugates of formula M(T-B) with high yields and purity.

A further object of the present invention is to provide carbohydrate Tcell epitope conjugates of formula (I) (M(T-B)_(n)) having a puritygrade superior than 95%, obtainable by the process according to theinvention.

These and other objects, features and advantages of the method accordingto the invention will be disclosed in the following detailed descriptionof the patent disclosure.

Thus, in one aspect, the present invention relates to a method forpreparing a carbohydrate T cell epitope conjugate of formula (I):

M(T-B)_(n)  (I)

wherein:

M is a dendrimeric poly-Lysine core;

T is a T cell epitope comprising a peptide;

B is a carbohydrate B cell epitope comprising at least one carbohydrateresidue (b);

n is an integer and represents the number of -T-B groups covalentlybonded to M;

Said method comprising the steps of:

i) coupling a protected carbohydrate B cell epitope (B_(Pr)) whichhydroxyl groups of the carbohydrate residue (b) are protected with aprotecting group (Pr),

-   -   with a compound M(T)_(n) thereby forming a carbohydrate T cell        epitope conjugate M(T-B_(Pr))_(n),    -   said protecting group (Pr) being selected from the group        consisting of allyl, p-methoxybenzyl (PMB), t-butyldimethylsilyl        (TBDMS), benzyloxymethyl (BOM), levulinyl (Lev), benzoyl (Bz),        2,5-difluorobenzoyl, chloroacetyl, benzyl (Bn) or an acetyl        (Ac),    -   or forming with two hydroxyl groups to which it is attached a        C₅-C₆ isopropylidene ketal or a C₅-C₆ cyclic alkylcarbonate;    -   and

ii) removing the protecting groups Pr from the obtained conjugateM(T-B_(Pr))_(n) thereby obtaining the carbohydrate T cell epitopeconjugate M(T-B)_(n).

Dendrimeric Poly-Lysine Core (M)

The poly-Lysine core of the conjugate of formula (I) is a dendrimericstructure, which may be represented as a star, having multiple branches(-T-B), which may be identical or not.

Such branches are covalently bonded to the NH₂ end of each lysineresidue of the dendrimeric core, notably by a peptide bond —NH—C(═O)—.

The valence m of the dendrimeric polyLysine core (M), i.e the number ofNH₂ end of each lysine residue is such that m≧n, preferably m=n, ndesignating the number of (-T-B) branches covalently bonded to M.

In another aspect, the number of (-T-B) branches n ranges from 4 to 16,notably from 4 to 8.

In a further aspect, the dendrimeric polyLysine core M comprises atleast 3 lysine residues, in particular 3 to 15 lysine residues, moreparticularly 3 to 7 lysine residues.

In an additional aspect, the conjugate M(T-B)_(n) is selected from thefollowing formulae (Ia) or (Ib):

wherein:

K is a lysine residue, and

T and B are as defined above.

Advantageously, dendrimeric structures (Ia) and (Ib) provide a highdensity of antigens at the surface of the dendrimeric polyLysine core M.

In a further aspect, M is (K)₂K-βAla-OH of the following formula:

(T-B) Branches

The presence of both carbohydrate B cell epitopes and T cell epitopes onthe conjugate of formula (I) renders the latter an efficient immunogen.

T Cell Epitopes

As used herein, T cell epitope means an antigen, in particular of apeptidic nature, capable of eliciting a T cell response.

Such epitopes are notably described in S. Stevanovic, “Identification ofTumour-associated T-cell epitopes for vaccine development”, NatureReviews, Vol. 2, July 2002, p. 1 to 7; J. H. Kessler, C. J. M. Melief,“Identification of T-cell epitopes for cancer immunotherapy”, Leukemia(2007) 21, 1859-1874, or in the Cancer immunity/peptide databasewebsite: http://www.cancerimmunity.org/peptidedatabase/tumorspecific.htm.

The T cell epitopes incorporated in the conjugate of formula (I) may bethe same or different, peptidic or not.

In a particular aspect, carbohydrate T cell epitope conjugates arecarbohydrate peptide conjugates. Peptidic T-cell epitopes can comprise 2to 50 amino-acids.

T cell epitopes may notably be selected amongst CD8⁺, or CD4⁺ T cellepitopes.

CD8⁺ T cell epitopes, recognized as tumoral markers, may be selectedfrom the group consisting of:

-   -   MUC-1 peptides (pancreas, breast)    -   MAGE 1 and 3 (melanoma, lung) (T. Boon et al. (1995), Immunology        Today, vol. 16 no 7, pp 334-336)    -   pme117/gp 100 (melanoma)    -   Tyrosinase (melanoma) BAGE (melanoma)    -   GAGE (melanoma) LB-33-B (melanoma)    -   CDK4    -   p185^(HER) (breast, ovary)    -   CEA MARTI/Melan-A (melanoma)    -   or selected in the group consisting of tumor antigens described        in A. Van Pel et al. (1995) Immunological. Reviews no 145, pp        229-250 or in P. G. Coulie (1995), Stem Cells, 13, pp 393-403.

In a particular aspect, T is or comprises a CD4⁺ T cell epitope, whichmay be notably a poliovirus (PV) protein fragment, a tetanus toxinfragment or a PADRE peptide.

As an example of CD4⁺ T cell epitope selected amongst poliovirus (PV)protein fragment, mention may be made of the synthetic peptide thatcorresponds to the 103-115 sequence of VP1 protein from poliovirus type1 (KLFAVWKITYKDT) (SEQ ID No. 4).

As example of CD4⁺ T cell epitope selected amongst tetanus toxinfragment, mention may be made of the following fragments:

-   -   830-844 sequence of the tetanus toxin (QYIKANSKFIGITEL) (SEQ ID        No. 1)    -   947-967 sequence of the tetanus toxin (FNNFTVSFWLRVPKVSASHLE)        (SEQ ID No. 2)    -   1273-1284 sequence of the tetanus toxin (GQIGNDPNRDIL) (SEQ ID        No. 3).

These peptidic T cell epitopes typically bind to a plurality of MHC(Major Histocompatibility Complex) human and murine molecules of classII avoiding in consequence the restriction problems encountered with theCD4+ T cellular response, associated with the polymorphism of the MI-ICmolecules existing between individuals. Moreover the use of tetanustoxin peptides should increase the immunogenicity of antigens present onthe conjugate of the present invention, as a result of the vaccinationof numerous individuals with the tetanus toxoid.

As further examples of peptide T-cell epitopes, reference may be made toS. Stevanovic, “Identification of Tumour-associated T-cell epitopes forvaccine development”, Nature Reviews, Vol. 2, July 2002, p. 1 to 7; J.H. Kessler, C. J. M. Melief, “Identification of T-cell epitopes forcancer immunotherapy”, Leukemia (2007) 21, 1859-1874, or in the Cancerimmunity/peptide database website: http://www.cancerimmunity.org/peptidedatabase/tumorspecific.htm.

Examples of non-peptidic T cell epitopes include notably:

-   -   fragments of pneumococcal type 4 polysaccharide, and        oligosaccharide tetanus toxoid conjugates as described        by C. C. A. M. Peeters (1991), in The Journal of Immunology,        146, 4309-4314,    -   meningococcal liposaccharides as described by A. F. M.        Verheul (1991) in Detection and Immunity, vol. 59, n° 10, pp.        3566-3573.

B Cell Epitopes

As used herein, B cell epitope means antigens capable of eliciting a Bcell response.

As used herein, a carbohydrate means a saccharide, notably mono-,oligo-, and polysaccharides.

In a preferred aspect, the carbohydrate residue (b) forming the B cellepitope of the conjugate of formula (I) is a N-acetylgalactopyranosylresidue, or a derivative thereof.

In a particular aspect, the carbohydrate residue (b) is attached to anamino acid, peptide, or lipid residue. In yet a further aspect, thecarbohydrate residue is an O-glycosyl amino acid or peptide. In afurther aspect, the B cell epitope is attached to the dendrimericstructure M(T)_(n) via said aminoacid or peptide.

The B cell epitope may comprise one or more carbohydrate residues (b),notably 1 to 10, in particular 1 to 6 carbohydrate residues.

Such B cell epitope may be selected from tumor (cancer) glycosidicantigens, notably from:

-   -   the glycolipid class, including acidic glycolipid such as, for        example, gangliosides GD2, GD3 and GM3 (melanoma) and neutral        glycolipids such as, for example, the Lewisy (Ley) (breast,        prostate, ovary) and the Globo H (breast, prostate, ovary)        antigens;    -   the O-glycosyl peptides (or aminoacid) class such as, for        example, the Tn antigen (α-GalNAc-Ser or α-GalNAc-Thr), TF        antigen (β-Gal-(1-3)-α-GalNAc-Ser or β-Gal-(1-3)-α-GalNAc-Thr),        two tumor markers frequently present in carcinomas but not        usually in normal tissues [Springer G. F. Science 224, 1198-1206        (1984)] (ovary, breast, lung), or di-Tn (α-GalNAc-Ser/Thr)₂,        tri-Tn (α-GalNAc-Ser/Thr)₃ or hexa-Tn (α-GalNAc-Ser/Thr)₆

The B cell epitope of the conjugate according to the present inventionmay also originate from capsular bacterial polysaccharides of, forexample, Neisseria meningitis, Haemophilus influenzae, Streptococcuspneumoniae, and of the Streptococcus group.

The polysaccharides are carbohydrate residues obtained by a syntheticprocess.

The B cell epitope of the present conjugate may be also of fungalorigin, such as for example, one isolated from the yeast Saccharomyces.

In a preferred aspect, the B cell epitopes of the conjugate of formula(I) are preferentially tumor markers, such as, for example, Tn and TFantigens.

It can be selected from the group comprising Tn, tri-Tn (Tn3), hexa-Tn(Tn6), or TF antigens.

In a further aspect, B is or comprises the carbohydrate residuesselected from the group consisting of:

-   -   α-GalNAc,    -   α-GalNAc-Ser,    -   α-GalNAc-Thr,    -   β-GalNAc,    -   β-GalNAc-Ser,    -   β-GalNAc-Thr,    -   β-Gal-(1-3)-α-GalNAc-Ser,    -   β-Gal-(1-3)-α-GalNAc-Thr,    -   (α-GalNAc-Ser/Thr)₂,    -   (α-GalNAc-Ser/Thr)₃, and    -   (α-GalNAc-Ser/Thr)₆,

In a preferred aspect, B is or comprises the residue(α-GalNAc-Ser/Thr)₃, most preferably(α-GalNAc)Ser-(α-GalNAc)Thr-(α-GalNAc)Thr.

In another preferred embodiment, the conjugate of formula (I) isMAG-Tn3.

Step i)

The method according to the present invention, comprises the step i) ofcoupling a protected carbohydrate B cell epitope (B_(Pr)) which hydroxylgroups of the carbohydrate residue (b) are protected with a protectinggroup (Pr), with a compound M(T)_(n) thereby forming a carbohydrate Tcell epitope conjugate M(T-B_(Pr)))_(n,)

-   -   said protecting group (Pr) being selected from the group        consisting of allyl, p-methoxybenzyl (PMB), t-butyldimethylsilyl        (TBDMS), benzyloxymethyl (BOM), levulinyl (Lev), benzoyl (Bz),        2,5-difluorobenzoyl, chloroacetyl, benzyl (Bn) or an acetyl        (Ac),    -   or forming with two hydroxyl groups to which it is attached a        C₅-C₆ isopropylidene ketal or a C₅-C₆ cyclic alkylcarbonate.

In a preferred aspect, Pr is benzyl (Bn) or acetyl (Ac).

In a particular aspect, step i) comprises the steps of:

a) Coupling a first protected carbohydrate residue (b_(Pr)) whichhydroxyl groups are protected with a protecting group (Pr), notablyselected from benzyl (Bn) or acetyl (Ac), with a compound M(T)_(n)thereby forming a carbohydrate T cell epitope conjugate M(T-b_(Pr))_(n);and optionally

b) repeating step a) with further protected carbohydrate residues(b_(Pr)) up to obtaining a protected carbohydrate conjugate of formula(II) M(T-B_(Pr))_(n).

Advantageously, it has been demonstrated that such protecting groups Prenable to control the coupling of each of the carbohydrate residues b,or of the B cell epitope B, with M(T)_(n) in step i). Further, it hasbeen shown that the removal of these protecting groups allows to obtainthe desired product, with an improved compromise between yield andpurity.

The hydroxyl groups of the carbohydrate residue can be protected by theabove mentioned protecting groups (Pr), notably by benzyl or acetylgroups, according to conventional methods.

Protected B cell epitopes B_(Pr) or carbohydrate residues (b_(Pr)) maybe commercially available or may be prepared from commercially availablestarting materials and/or according to conventional methods.

In a preferred aspect, the dendrimeric polyLysine core M and thus thesubsequent M(T)_(n) building block are immobilized on a solid support,thus enabling iterative solid phase peptide synthesis.

As an example of solid support, mention may be made of polystyrene resinfunctionalized with p-benzyloxybenzyl alcohol (Wang resin) on whichFmoc-β-Ala-groups may then be grafted or those sold under the trade nameFmoc-β-Ala-TentaGel R Trt. The M core may notably be attached via aβ-Ala-OH residue. The resin substitution ratio, i.e the grafting ratioof the resin by Fmoc-β-Ala- groups may range from 0.2 to 0.05 mmol/g,preferably from 0.10 to 0.13 mmol/g.

In a particular aspect, b_(Pr) is a protected O-glycosyl amino acid orpeptide. Protected O-glycosyl peptide may be coupled to the M(T)_(n)building block by successively introducing the protected constitutiveO-glycosyl amino acid residues b_(Pr).

In this regard, the solid phase peptide and glycopeptide synthesis maybe performed using the standard Fmoc chemistry protocol [5] and [6].N-α-Fmoc aminoacids and glycosylated aminoacids or peptides areincorporated stepwise in the peptide chain.

Thus, step i) may be performed by reacting a first protected N-α-FmocO-glycosyl amino acid b_(Pr) with the M(T)_(n) building block. Morespecifically, the carboxylic group (COOH) of the first O-glycosyl aminoacid b_(Pr) is reacted with the NH₂ end of each of the T branches,thereby forming a peptide covalent bond (—C(C═O)NH—).

The Fmoc is cleaved, for example in the presence of 20% of piperidine inDMF or NMP. Then a second protected N-α-Frnoc O-glycosyl amino acidb_(Pr) may be similarly reacted with the NH₂ group of the firstprotected amino acid residue, and so on.

Thus, when the B cell epitope comprises several carbohydrate residues(b), step i) of the method according to the invention may comprise thestep of repeating the coupling according to step a) up to obtaining thecarbohydrate T cell epitope conjugate M(T-B_(Pr))_(n).

These peptide coupling may be carried out in a polar aprotic solventsuch as DMF or NMP, in the presence of coupling reagents such as HATUand DIPEA or DIC/HOBt, and PyBOP.

Step ii)

In a particular aspect, Pr is benzyl. In that case, the deprotectionstep ii) may be carried out in the presence of TfOH or by a catalytichydrogenation.

In a particular aspect, step ii) is a catalytic hydrogenation.

In a preferred aspect, the catalytic hydrogenation is carried out in thepresence of Pd/C, notably of 10% Pd/C (% w/w), as a catalyst. The weightratio of the conjugate of formula (II)/catalyst may vary from 10/2 to10/10, and is preferably of about 10/8. The catalyst may be addedportionwise over a long period.

The catalytic hydrogenation is preferably carried out in NMP/H₂O,notably in a volume ratio of 87.5/12.5, as a solvent.

The catalytic hydrogenation reaction is preferably carried out at atemperature ranging from 20 to 40° C., in particular at about 37° C.

The catalytic hydrogenation reaction is preferably carried out under apressure ranging from 1 to 10 bar, more preferably at about 5 bar.

In another aspect, step ii) is carried out in the presence of TfOH.

Preferably, the conjugate of formula (II) is reacted with TfOH, in thepresence of TFA, DMS and m-cresol. The relative ratio ofTfOH/TFA/DMF/m-cresol may be of 1/5/3/1 v/v/v/v.

In another aspect, the protecting group Pr is acetyl.

The deprotection of acetyl protecting groups in step ii) is preferablyperformed in the presence of hydrazine, in a protic polar solvent, forexample an alcohol such as methanol. This reaction may be performed atroom temperature, i.e between 15 and 25° C.

The molar ratio of hydrazine relative to the compound of formula (II)may vary from 100 to 1500 molar equivalents.

The deprotection of acetyl may alternatively be performed in thepresence of MeONa, notably in MeOH as a solvent, at room temperature,i.e between 15 and 25° C.

In a particular aspect, when immobilized in a solid support, theconjugate of formula (II) obtained at the end of i) is preliminarycleaved from the solid support, before performing the deprotection stepii). Such cleavage may be performed in the presence of TFA and TIS inwater, for example with the following volume ratio 95/2.5/2.5 v/v/v.

Step iii)

The method according to the invention may further comprise a step iii)subsequent to step ii) consisting in one or more purification steps,notably by reverse phase high-performance liquid chromatography(RP-HPLC).

Step iv)

The method according to the invention may further comprise a subsequentstep iv) of recovering the product.

M(T)_(n) Synthesis

In a particular aspect, the method according to the invention furthercomprises the step of preparing the conjugate M(T)_(n).

In a particular embodiment, the conjugate M(T)_(n) is prepared startingfrom the dendrimeric polyLysine core and by introducing stepwise theN-protected amino acid residues constituting the peptide T cell epitope.The N-protected amino acid residues are notably Fmoc amino acidresidues.

The amino acid couplings may be performed in a polar aprotic solventsuch as DMF, in the presence of one or more peptide coupling reagentssuch as DIC, HOBt, PyBOP, HATU or DIPEA. The combinations (DIC/HOBt andPyBOP) or alternatively (HATU/DIPEA) are particularly preferred.Alternative coupling reagents are also disclosed in E. Valeur; M.Bradley, Chem Soc Rev (2009) 38, 606; A. El-Faham et al. Chem Eur J(2009) 15, 9404 or R. Subiros-Funosas et al. Org Biomol Chem (2010) 8,3665.

Following each peptide coupling, the N-amino acid protecting groups areremoved. As an example, Fmoc protecting groups can be removed in thepresence of piperidine in a polar aprotic solvent such as DMF.

As regards the synthesis of the peptide fragment SEQ ID no. 1 the aminoacid residues AA⁹⁻¹⁰ and AA¹⁵⁻¹⁶ can be incorporated as pseudo-prolinedipeptides. Advantageously, the incorporation of such dipeptidesdemonstrated a significant impact on the crude quality of the product.

M Synthesis

In a particular aspect, the method according to the invention furthercomprises the step of preparing a dendrimeric polyLysine core M.

The dendrimeric polyLysine core M may be prepared according to themethod disclosed in U.S. Pat. No. 6,676,946.

Carbohydrate T Cell Epitope Conjugate M(T-B)_(n)

In another aspect, the present invention advantageously provides acarbohydrate T cell epitope conjugate M(T-B)_(n) having a grade ofpurity ≧95% obtainable according to the method of the invention.

Such a purity grade may be obtained by performing a purification step(iii) after step (ii), notably a reverse phase high-performance liquidchromatography (RP-HPLC). As an example, RP-HPLC may be performed with alow-granulometry column, notably having a granulometry inferior to 15μm, notably of about 10 μm or inferior to 5μ and/or having a pore sizeof about 300 Å or less, notably less than 200 Å, in particular less than100 Å. The stationary phase may be a reversed phase based on silica gelgrafted by octadecyl groups (also called C18 silica). Elution may beperformed with water (0.1% TFA)/acetonitrile with a shallow gradient,for instance from 70/30 to 60/40 over a period of about 20 minutes.

The purity grade of the conjugate of formula (I) can be determined byany conventional method, notably by RP-HPLC.

The purity is preferably ≧96%, notably ≧98%, and advantageously ≧99%.

Carbohydrate T Cell Epitope Conjugate M(T-B_(Pr))_(n)

In an additional aspect, the present invention provides a carbohydrate Tcell epitope conjugate of formula (II):

M(T-B_(Pr))_(n)  (II)

Wherein

-   -   M is a dendrimeric poly-Lysine core;    -   T is a T cell epitope, preferably comprising a peptide residue;    -   B_(Pr) is a protected carbohydrate B cell epitope comprising at        least one carbohydrate residue (b) which hydroxyl groups are        protected by a Pr group,    -   said Pr group being selected from the group consisting of allyl,        p-methoxybenzyl (PMB), t-butyldimethylsilyl (TBDMS),        benzyloxyrnethyl (BOM), levulinyl (Lev), benzoyl (Bz),        2,5-difluorobenzoyl, chloroacetyl, benzyl (Bn) or an acetyl        (Ac), or forming with two hydroxyl groups to which it is        attached a C₅-C₆ isopropylidene ketal or a C₅-C₆ cyclic        alkylcarbonate    -   and    -   n is an integer and represents the number of -T-B groups        covalently bonded to M.

In a particular aspect, Bp, is a protected (α-GalNAc-Ser/Thr)3.

In an additional aspect, Pr is benzyl or acetyl

In a further aspect, M is HO-βAla-K(K)₂.

In another aspect, T is QYIKANSKFIGITEL (SEQ ID No. 1).

In another object, the invention provides a use of a carbohydratepeptide conjugate M(T-B_(Pr))_(n) for preparing a carbohydrate peptideconjugate M(T-B)_(n), M(T-B_(Pr))_(n) and M(T-B)_(n) being as definedabove.

Other features of the invention will become apparent in the course ofthe following descriptions of exemplary embodiments. These examples aregiven for illustration of the invention and are not intended to belimiting thereof.

FIGURES

FIG. 1: MAG-Tn3 synthesis according to protocol A of the method of theinvention. The molar equivalents are indicated relative to amino group.The AA⁹⁻¹⁰ and AA¹⁵⁻¹⁶ are incorporated as pseudo-Pro dipeptides.

FIG. 2: MAG-Tn3 synthesis according to protocol B of the method of theinvention. The molar equivalents are indicated relative to amino group.The AA⁹⁻¹⁰ and AA¹⁵⁻¹⁶ are incorporated as pseudo-Pro dipeptides.

ABBREVIATIONS

AA amino acid

Ac acetyl

AcOH acetic acid

Bn benzyl

Boc tert-butoxycarbonyl

tBu tert-butyl

DIC N,N′-diisopropylcarbodiimide

DIPEA diisopropylethylamine

DIPE diisopropyl ether

DMAP 4-dimethylaminopyridine

DMF dimethylformamide

DMS dimethylsulfide

DVB divinylbenzene

EtOH ethanol

FA formic acid

Fmoc 9-fluorenylmethoxycarbonyl

HATU 2-(1H-9-azabenzotriazole-1-yl)-1,1,3,3-tetramethyluroniumhexafluorophosphate

HOBt N-hydroxybenzotriazole

HPLC/MS high performance liquid chromatography/mass spectroscopy

MAG multiple antigenic glycoppeptide

MeOH methanol

MeONa sodium methylate

ESMS electrospray mass spectrometry

MW molecular weight

NMP N-methylpyrrolidone

NMR nuclear magnetic resonance

PyBOP benzotriazole-1-yl-oxy-tris-pyrrolidino-phosphoniumhexafluorophosphate

RP-HPLC reverse phase high-performance liquid chromatography

RT room temperature

SELDI-TOF MS surface-enhanced laser desorption/ionization time-of-flightmass spectrometry

TBS tert-butyldimethylsilyl

TFA trifluoroacetic acid

TfOH trifluoromethanesulfonic acid

THF tetrahydrofuran

TIS triisopropylsilane

TMSBr trimethylsilyl bromide

Trt trityl

EXAMPLES Example 1 Preparation of MAG-Tn3 Via Protocol A and B

General Methods

The synthesis of 6 was performed stepwise on solid-phase using Fmocchemistry. Amino acid side chain protective groups used were Trt on Glnand Asn, Boc on the Lys⁷ and Lys¹¹, tBu on Tyr, Ser and Thr, OtBu onGlu. For the Lys¹⁹ and Lys²⁰, the protective groups were Fmoc.

The net peptide contents were determined by nitrogen analysis orquantitative amino acid analysis using a Beckman 6300 analyser afterhydrolysis of the compounds with 6N HCl at 110° C. for 20 h.

The HPLC/MS analyses were performed on an Alliance 2695 system coupledto a UV detector 2487 (220 nm) and to a Q-Tofmicro™ spectrometer(Micromass) with an electrospray ionisation (positive mode) source(Waters). The samples were cooled to 4° C. on the autosampler. Thelinear gradient was performed with acetonitrile+0.025% FA(A)/water+0.04% TFA+0.05% FA (B) over 20 min. The column was a Zorbax300SB C18 (3.5μ, 3×150 mm) (Agilent) (gradient 13-53% A) or a XBridge™BEH130 C18 (3.5μ, 2.1×150 mm) (Waters) (gradient 15-40% A). Thetemperature of the source was maintained at 120° C. and the desolvationtemperature at 400° C. The cone voltage was 40V.

The ESMS analyses were recorded in the positive mode by direct infusionin the same mass spectrometer. The samples were dissolved at ˜5 μMconcentration in water/acetonitrile (1/1) with 0.1% formic acid.

The SELDI-TOF analyses were performed on a PCS 4000 mass spectrometer(Bio-Rad Labs). H4 ProteinChip array surfaces were activated with 14CH₃CN. Spots were incubated with the reaction mixture (2.5 μL, 1 mg/mL)in a box at RT for 20 min. They were then washed with the reactionbuffer (3×1 min) and H₂O (3×1 min). The matrix (2×0.6 μL of sinapinicacid saturated in 50% CH₃CN/0.5% TFA) was applied on each spot andallowed to air-dry. Spectra were generated from each array spot with alaser setting ˜3 μJ. The instrument was externally calibrated withbovine ubiquitin, bovine cytochrome C, β-lactoglobulin with the matrixand the settings as described above.

The purity of 6 was analyzed by RP-HPLC using an Agilent 1200 pumpsystem with a UV detector at 220 nm. The column was a Zorbax 300SB C18(3.5μ, 3×150 mm) (Agilent) and the gradient was performed withacetonitrile+0.1% TFA (A)/water+0.1% TFA (B) over 40 min, from 13 to 53%A (0.8 mL/min, retention time 20.5 min).

The molar equivalents of all reagents are indicated relative to aminogroups. The molar amounts of the protected intermediates 4 and 5 arecalculated based on the starting Fmoc-β-Ala-resin 1 substitution. Theoverall yields (Table) include all the synthetic steps from 1. They werecalculated on the net peptide content of the final product 6 from theFmoc-β-Ala-resin 1 substitution.

Protocol A (FIG. 1)

Fmoc-β-Ala-Resin (Low-Substituted Resin) 1

2 g of p-benzyloxybenzyl alcohol resin (Wang resin, 0.91 mmol/g, 100-200mesh, polymer matrix: copoly(styrene-1% DVB), Novabiochem) were swelledin DMF (Applied Biosystems) for 1 h in a dry round-bottomed flask. 311mg (1 mmol) of dry Fmoc-β-Ala-OH (Novabiochem, Merck Chemicals Ltd) weredissolved in 8 mL of anhydrous CH₂Cl₂ (Acros). Four drops of DMF wereadded to complete the dissolution. After the addition of 77 μL (0.5mmol) of DIC (Fluka), the reaction mixture was stirred for 20 min underargon, at room temperature. The reaction mixture was evaporated todryness and the rotary evaporator opened under argon. The residue wasdissolved in the minimum volume of DMF (6 mL) and the solution was addedto the resin. 6 mg (0.05 mmol) of DMAP (Acros) dissolved in 0.5 mL ofDMF were added and the suspension was stirred gently for 2 h at roomtemperature.

The resin substitution rate was measured by UV analysis of a resinsample according to the following procedure. 2 to 6 mg of resin weretransferred with a Pasteur pipette to a small sintered glass funnel. Theresin was washed with DMF, CH₂Cl₂ (Carlo Erba) and dried. The resin wastransferred in an UV cell, precisely weighted and then added with 2.8 mLof 20% piperidine (Aldrich) in DMF. The suspension was agitated with theaid of a Pasteur pipette for 2 min. The absorbance was read at 300.5 nm(ε=7800) with the reference cell containing 20% piperidine in DMF. Theextent of loading was found to be 0.1 mmol/g.

The resin was washed three times with DMF. The residual hydroxyl groupswere capped using the following protocol. The resin was resuspended in13 mL of DMF. 1.55 mL (16.4 mmol) of Ac₂O (Sigma) in 1 mL of DMF, andthen 660 mg (5.41 mmol) of DMAP in 1 mL of DMF were added. After gentlystirring for 30 min at room temperature, the suspension was filtered ina sintered glass funnel, successively washed three times by DMF, threetimes by CH₂Cl₂ and then was dried overnight in a desiccator. The resin1 was stored at 4° C.

[QYIKANSKFIGITEL]₄-K₂-K-β-Ala-Resin (protected peptide) 2

The tetravalent peptide was synthesized from 250 mg (25 μmol) ofFmoc-β-Ala-resin 1 on an Applied Biosystems peptide synthesizer 433Ausing Fmoc chemistry. The Applied standard synthesis protocol wasfollowed except for an additional washing step after each coupling step.Briefly, the Fmoc groups were removed with 22% piperidine in NMP(Applied Biosystems) and the deprotection was monitored by conductivity.The lysine core was constructed by successively coupling two levels ofFmoc-Lys(Fmoc)-OH (Applied Biosystems) (1^(st) cycle: 40 eq, 2^(nd)cycle: 20 eq) using HATU (Applied Biosystems) (1^(st) cycle: 40 eq,2^(nd) cycle: 20 eq)/DIPEA (Applied Biosystems) (1^(st) cycle 80 eq,2^(nd) cycle: 40 eq) as the coupling reagents and NMP as solvent (Note:the use of this very large excess of reagents should be not necessaryfor the efficiency of the reaction and is only due to the fact that theprepacked cartridges are filled with 1 mmol of amino acid). The stepwiseintroduction of the subsequent Fmoc-protected amino acids (AppliedBiosystems, 10 eq/amine) carrying standard side-chain protective groupswas performed with HATU (10 eq/amine)/DIPEA (20 eq/amine) in NMP. The AAin positions 15-16 and 9-10 were incorporated as, respectively,Fmoc-Ile-Thr(Ψ^(Me,Me)pro)-OH and Fmoc-Asn(Trt)-Ser(Ψ^(Me,Me)pro)-OH (10eq/amine) (Novabiochem, Merck Chemicals Ltd) with HATU (10 eq/amine) andDIPEA (20 eq/amine).

[S(α-D-GalNAc(OBn)₃)-T(α-D-GalNAc(OBn)₃)-T(α-D-GalNAc(OBn)₃)-QYIKANSKFIGITEL]₄-K₂-K-β-Ala5

Starting from 2 (25 μmol), the glycosylated building blocks wereincorporated manually: Fmoc-T(α-D-GalNAc(OBn)₃)—OH (Ficher Chemicals AG)(1^(st) cycle), Fmoc-T(α-D-GalNAc(OBn)₃)—OH (2^(nd) cycle) andFmoc-S(α-D-GalNAc(OBn)₃)—OH (Ficher Chemicals AG) (3^(rd) cycle).Briefly, the dry building block (0.3 mmol, 3 eq/free amino group) wasdissolved in the minimum amount of DMF (˜2 mL). A solution of 55 mg(0.145 mmol) of HATU (Novabiochem) in 0.5 mL DMF was added and theresulting mixture was added to the resin. After adding 52 μL (0.3 mmol)of DIPEA (Aldrich), the suspension was mechanically stirred. The threecoupling steps were monitored by the Kaiser test [1] and were completed,respectively, in 1 h, 1 h and 1 h. After each coupling steps, the resinwas washed with DMF (four times). All Fmoc cleavages were carried out bytreatment of the resin with 20% piperidine in DMF. Following eachdeprotection, the resin was successively washed by DMF (six times),CH₂Cl₂ (six times), and DMF (six times). At the end of the synthesis,the resin was extensively washed with DMF and CH₂Cl₂, and dried in adesiccator. 10 mL of TFA (Applied Biosystems)/water/TIS (Acros)(95/2.5/2.5 v/v/v) were added to the resin at 4° C. and the mixture wasstirred for 1 h30 at room temperature. After filtration of the resin,the solution was concentrated and the crude product precipitated withdiethyl ether. After centrifugation, the pellet was dissolved in waterand lyophilized to yield 229 mg of the crude glycopeptide 5.

[S(α-D-GalNAc)-T(α-D-GalNAc)-T(α-D-GalNAc)-QYIKANSKFIGITEL]₄-K₂-K-β-Alaor MAG-Tn3 6

From 5,

With TfOH [2-4]

200 mg (0.014=101) of 5 were dissolved in 2.96 mL of TFA, 1.78 mL of DMS(Sigma-Aldrich) and 587 μL of metacresol (Sigma-Aldrich) at RT. Thesolution was cooled to −10° C. and 587 μL of TfOH (Fluka) was added andthe mixture was stirred 1 h15 at −10° C. (TfOH/TFA/DMS/m-cresol 1/5/3/1v/v/v/v). The product was precipitated with diethyl ether and, aftercentrifugation, the pellet was dissolved in water and lyophilized toyield 372 mg of the crude glycopeptide. The product was dissolved in 7.7mL of 0.05M ammonium acetate buffer and the pH adjusted to 7 with 1Mammonia. After 1 h at room temperature, the solution was lyophilized toyield to 412 mg of the crude product. The product was purified byRP-HPLC using an Agilent 1200 pump system with a UV detector at 230 nm.The column was a Zorbax C18 (5μ, 300 Å, 9.4×250 mm) (Agilent) and thegradient was performed with water (0.1% TFA)/acetonitrile over 20 min,from 73/27 to 60/40. The purification gave 3.9 mg (net peptide content)of 6 in 95.90% purity. The overall yield is 1.6%.

Protocol B (FIG. 2)

[QYIKANSKFIGITEL]₄-K₂-K-β-Ala-Resin (protected peptide) 2

Until the incorporation of Tyr⁵, the tetravalent peptide was synthesizedfrom 36.9 g (4.8 mmol) of Fmoc-β-Ala-Tentagel R Trt resin 1 (0.13mmol/g) (Rapp Polymere) on a manual peptide synthesizer equipped with aSchmizo reactor. Before the elongation process, the resin was swelled inDMF for 2 to 3 hours and was washed with 240 mL of DMF (three times, 2min/cycle). Following each coupling, the Fmoc groups were removed with20% piperidine in 240 mL of DMF (three steps, 20 min each). In the caseof Glu¹⁷, Asn⁹ and Gln⁴, 2% HOBt was added to the deprotection solution.Following each deprotection, the resin was successively washed by 240 mLof DMF (4 times, 2 min/cycle), 240 mL of 2% HOBt in DMF (twice, 5min/cycle), and 240 mL of DMF (twice, 2 min/cycle).

The amino acid couplings (1.5 to 2 eq/amine) were performed in DMF (111mL) at room temperature with DIC/HOBT (1.5 to 2 eq each/amine) (seedetails below). The AA in positions 15-16 and 9-10 were incorporated as,respectively, Fmoc-Ile-Thr(Ψ^(Me,Me)pro)-OH andFmoc-Asn(Trt)-Ser(Ψ^(Me,Me)pro)-OH. After 30 min, a fresh portion of DIC(1.5 to 2 eq) was added to the reaction mixture. The coupling steps weremonitored by the Kaiser test [1]. From Leu¹⁸ to Ser¹, after 1 h couplingwith DIC/HOBT (in equal amount), PyBOP reagent was added (see detailsbelow) and the pH was adjusted to 7 by dropwise addition of DIPEA. After30 min, the resin was washed with 240 mL of DMF (5 times, 2 min/cycle)and an acetylation step was carried out from Leu¹⁸ to Thr². Theacetylation was performed at room temperature with acetic anhydride (1eq/amine) in the presence of pyridine (1 eq/amine) in 111 mL of DMF.After 20 min, the resin was washed with 240 mL of DMF (6 times, 2min/cycle). After the incorporation of Tyr⁵, the resin was extensivelywashed with 240 mL of DMF (8 times, 2 min/cycle) and 240 mL of CH₂Cl₂ (8times, 2 min/cycle), before drying.

After the incorporation of Tyr⁵, the assembly was pursued on a 0.15 mmolscale or a 4.65 mmol scale using the same protocole and afforded thepeptide-resin 2 for, respectively, 4 and 5.

DIC/HOBt:1/1 Coupling PyBOP Amino acids (eq/amine, reaction (eq/(eq/amine, mmol) mmol) (min) amine) 20. Fmoc-Lys(Fmoc)—OH 1.75, 2.1   600.5 (1.75, 2.1) 19. Fmoc-Lys(Fmoc)—OH 2, 4.8 105 1 (2, 4.8) 18.Fmoc-Leu-OH (2, 9.6) 2, 9.6 60 1 17. Fmoc-Glu(OtBu) (2, 9.6) 2, 9.6 60 116-15. Fmoc-Ile- 1.5, 7.2   60 0.5 Thr(Ψ^(Me-Me)pro)-OH (1.5, 7.2) 14.Fmoc-Gly-OH (2, 9.6) 2, 9.6 60 1 13. Fmoc-Ile-OH (2, 9.6) 2, 9.6 60 112. Fmoc-Phe-OH (2, 9.6) 2, 9.6 60 1 11. Fmoc-Lys(Boc)—OH 2, 9.6 60 1 (2eq, 9.6 mmol) 10-9. Fmoc-Asn(Trt)- 1.5, 7.2   60 0.5Ser(Ψ^(Me-Me)pro)-OH (1.5, 7.2)  8. Fmoc-Ala-OH (2, 9.6) 2, 9.6 60 1  7.Fmoc-Lys(Boc)—OH 2, 9.6 60 1 (2, 9.6)  6. Fmoc-Ile-OH (2, 9.6) 2, 9.6 601  5. Fmoc-Tyr(tBu)—OH 2, 9.6 60 1 (2, 9.6)  4. Fmoc-Gln(Trt)-OH (2,1.2) or 60 1 (2, 1.2 for 4) or (2, 37.2) (2, 37.2 for 5)

[S(α-D-GalNAc(O(Ac)₃)-T(α-D-GalNAc(OAc)₃)-T(α-D-GalNAc(OAc)₃)-QYIKANSKFIGITEL]₄-K₂-K-β-Ala4

The synthesis was performed from 2 (0.15 mmol) as previously describedfor 2. The coupling steps were performed with the following AA buildingblocks [5] and reagents.

DIC/HOBt:1/1 Coupling PyBOP Amino acids (eq/amine, reaction (eq/(eq/amine, mmol) mmol) (min) amine) 3. Fmoc-Thr(α-D- 1.5, 0.9 60 0.5GalNAc(OAc)3)—OH (1.5, 0,9) 2. Fmoc-Thr(α-D- 1.5, 0.9 60 0.5GalNAc(OAc)3)—OH (1.5, 0.9) 1. Fmoc-Ser(α-D- 1.5, 0.9 60 0.5GalNAc(OAc)3)—OH (1.5, 0.9)

At the end of the synthesis, the glycopeptide-resin (0.15 mmol) wassuspended in a TFA/TIS/H₂O (95/2.5/2.5 v/v/v) (10 mL/g ofglycopeptide-resin) and stirred for 1 h at 20° C.±2° C. Afterfiltration, the resin was washed twice with the same TFA mixture (2 mL/gof glycopeptide-resin per wash). The filtrates and the washes weregathered and stirred for additional 30 min at 20° C.±2° C. Afterconcentration (bath temperature ≦35° C.), the crude product wasprecipitated with DIPE (˜35 mL/g of glycopeptide-resin). Afterfiltration and washing with DIPE, the solid was dried (t°≦30° C.) andgave 750 mg of crude 4.

ESMS: 12409.589 (C₅₅₃H₈₅₅N₁₀₇O₂₁₃ calcd 12410,465)

[S(α-D-GalNAc(OBn)₃)-T(α-D-GalNAc(OBn)₃)-T(α-D-GalNAc(OBn)₃)-QYIKANSICFIGITEL]₄-K₂-K-β-Ala5

The synthesis was performed from 2 (4.65 mmol) as previously describedfor 2. The coupling steps were performed with the following AA buildingblocks (Ficher Chemicals AG) and reagents. At the end of the synthesis,84.87 g of glycopeptide-resin were obtained.

DIC/HOBt:1/1 Coupling PyBOP Amino acids (eq/amine, reaction (eq/(eq/amine, mmol) mmol) (min) amine) 3. Fmoc-Thr(α-D- 1.5, 27.9 60 0.5GalNAc(OBn)3)—OH (1.5, 27.9) 2. Fmoc-Thr(α-D- 1.5, 27.9 60 0.5GalNAc(OBn)3)—OH (1.5, 27.9) 1. Fmoc-Ser(α-D- 1.5, 27.9 60 0.5GalNAc(OBn)3)—OH (1.5, 27.9)

The glycopeptide-resin (20 g, 1.096 mmol) was treated as previouslydescribed for 4 and afforded 9.95 g of crude 5.

ESMS: 14141.433 (C₇₃₃H₉₉₉N₁₀₇O₁₇₇ calcd 14141,610)

Note: This protocol gave a comparable crude compound as that obtainedaccording to protocol A, i.e. starting from Fmoc-β-Ala-p-benzyloxybenzylalcohol resin (Wang resin) (see above).

[S(α-D-GalNAc(OH)₃)-T(α-D-GalNAc(OH)₃)-T(α-D-GalNAc(OH)₃)-QYIKANSKFIGITEL]₄-K₂-K-β-Alaor MAG-Tn3 6

From 4

With Hydrazine[7]

100 mg (20 μmol) of 4 were dissolved in 3.2 mL of MeOH. 567 μL (11.3mmol) of hydrazine monohydrate were added and the solution was stirredat room temperature. After 2 h30, the solution is cooled to 0° C. and3.2 mL of acetone were added. After 1 h, the solution was concentratedand co-distilled five times with acetone. The crude glycopeptide waslyophilized to yield 117 mg. The product was purified by RP-HPLC usingan Agilent 1200 pump system with a UV detector at 230 nm. The column wasa Zorbax C18 (5μ, 300 Å, 9.4×250 mm) (Agilent) and the gradient wasperformed with water (0.1% TFA)/acetonitrile over 20 min, from 72/28 to62138. The purification gave 5.8 mg (net peptide content) of 6 in 96.4%purity. The overall yield is 2.7%.

With MeONa

24 mg (4.8 μmol) of 4 were dissolved in 3.2 mL of MeOH. The pH wasadjusted to 14 (pH meter, moist pH paper 10.5) with 1% MeONa in MeOH andthe solution stirred at RT. The reaction was monitored by RP-HPLC. After2 h, the reaction is neutralized with dry ice and evaporated to dryness.The crude peptide was dissolved in 1% aqueous TFA and lyophilized. Theproduct was purified by RP-HPLC using an Agilent 1200 pump system with aUV detector at 230 nm. The column was a Kromasil C4 (5μ, 100 Å, 10×250mm) (AIT) and the gradient was performed with 0.1% aqueous TFA(VWR)/acetonitrile (Carlo Erba) over 30 min, from 73/27 to 62/38. Thepurification gave 754 μg (net peptide content) of 6 in 91.4% purity. Theoverall yield is 1.4%.

From 5,

With H₂

10 g (1.1 mmol) of 5 were dissolved in 800 mL of NMP/H₂O 87.5/12.5.After addition of 4 g of 10% Pd/C type 39 (Johnson Matthey), thereaction was stirred at 37° C. and 5 bar for 170 h. Two additionalamounts of catalyst were added portionwise after 72 h (2 g) and 120 h (2g). At the end of the reaction, the catalyst was filtrated on celite andwashed with NMP/H₂O 87.5/12.5. The resulting filtrate was gathered withother filtrates issued from similar reaction (1.35 mmol in total). Afterdilution with H₂O (until NMP/H₂O 10/90), the filtrates were purified byRP-HPLC in two steps. The primary purification was carried out on aVydac C18 column (300 Å, 10-15 μm, 50 mL/mn) with TFA/H₂O/CH₃CN0.1/94.9/5.0 v/v/v (A) and with TFA/H₂O/CH₃CN 0.1/49.9/50.0 v/v/v (B).The gradient was 0% B over 15 min, 0-40% B over 5 min, 40-80% B over 60min. The secondary purification was carried out on a Vydac C18 column(300 Å, 10-15 μm, 50 mL/mn) with AcOH/H₂O/CH₃CN 0.5/94.5/5.0 v/v/v (A)and with AcOH/H₂O/CH₃CN 0.5/49.5/50.0 v/v/v (B). The gradient was 0% Bover 15 min, 0-20% B over 5 min, 20-60% B over 60 min. Afterconcentration by RP-HPLC on a Daisogel SP-300-10-ODS-AP column (20mL/mn, isocratic TFA/H₂O/CH₃CN 0.1/49.9/50.0 v/v/v), the solution wasevaporated on rotary evaporator and lyophilized to afford 225 mg (netpeptide content) of 6 in 95.3% purity. The overall yield is 1.5%.

ESMS: 10897.387 (C₄₈₁H₇₈₃N₁₀₇O₁₇₇ calcd 10897,123)

CONCLUSION

The obtained results are summarized in the following table:

Initial process I¹ New process II Carbohydrate None (H) TBS Ac Bnprotective group (R) Deprotection — TFA NH₂—NH₂ TfOH H₂ method Overallyield² 1-10 mg scale — 2.7% (96.4%) 1.6% (95.9%) 1.5% (95.3%) (Purity)³3% (94.5%) >10 mg scale <1% (<95%) Comment Impurities and No expectedScale ~5 mg Compromise Scale 225 mg Scale⁴ reproducibility compound(partial between complete issues during deprotection) deprotection andscale-up => new Impurities++ degradation. synthesis route Scale ~5 mgwith carbohydrate protection ¹ref 5 and 9, (Ref 11 of WO 9843677Multiple antigen glycopeptide carbohydrate, vaccine comprising the sameand use thereof) ²calculated on the net peptide content from theFmoc-βAla-resin substitution (includes all the synthesis steps from 1).³as determined by RP-HPLC: Column Zorbax 300SB C18 (3.5μ, 3 × 150 mm)(Agilent), 0.8 mL/min, A: acetonitrile + 0.1% TFA, B: water + 0.1% TFA,gradient 13% to 53% of A over 40 min, detection at 220 nm. ⁴Refers tothe final product (net peptide content)

Compared to the initial synthesis using unprotected carbohydratesynthons (FIGS. 1 and 2), the new process (involving protectedcarbohydrates, II, FIGS. 1 and 2) allows to:

-   -   minimize the synthesis side-products    -   improve the process repeatability    -   scale-up the synthesis in a repeatable manner

Among the tested protocols in the new process (Table, FIGS. 1 and 2),three emerge as the best strategies: Ac/Hydrazine, Bn/TfOH and Bn/H₂(protecting group/deprotection method) (Table). They all led to theMAG-Tn3 with a purity ≧95%, in a repeatable manner.

The Bn/TfOH method afforded the MAG-Tn3 with an overall yield of 1.6%.This method relies on a compromise between complete deprotection anddegradation. Alternatively, the Bn/H₂ method afforded the MAG-Tn3 withsimilar yield (1.5%) and, most importantly, the process has beenvalidated on a 225 mg scale. Finally the Ac/hydrazine method gave thehighest overall yield (2.7%, compared to 1.6% and 1.5%).

A MAG-Tn3 based on another peptide (PVKLFAVWKITYKDT) (SEQ ID No. 4) hasalso been prepared according to the method of invention (Ac/Hydrazine,Bn/TfOH).)

Example 2 Influence of the Resin Substitution Ratio and of the Nature ofthe Stationary Phase Used for the Purification of MAG-Tn3

MAG-Tn3 was prepared according to protocol B from a polystyrene resinfunctionalized with Fmoc-β-Ala (sold under the trade nameFmoc-β-Ala-TentaGel R Trt), with two different substitution ratios: 0.13or 0.1 mmol/g (namely the number of Fmoc-β-Ala grafted groups relativeto the weight of the non grafted resin).

The purification of the crude MAG-Tn3 was then performed by RP-HPLC onthree distinct stationary phases (reversed phases) based on a silica gelgrafted by octadecyl groups, namely Vydac®, Jupiter® and Daisogel®. Theprimary purification was carried out with TFA/H₂O/CH₃CN 0.1/94.915.0v/v/v (A) and with TFA/H₂O/CH₃CN 0.1/49.9/50.0 v/v/v (B). The gradientwas 0% B over 15 min, 0-40% B over 5 min, 40-80% B over 60 min. Thesecondary purification was carried out with AcOH/H₂O/CH₃CN 0.5/94.5/5.0v/v/v (A) and with AcOH/H₂O/CH₃CN 0.5/49.5150.0 v/v/v (B). The gradientwas 0% B over 15 min, 0-20% B over 5 min, 2060% B over 60 min.

The results are reported in the following table.

Resin Purification Overall MAG-Tn3 substitution stationary QuantityPurity yield batch (mmol/g) phase (g)^(a) (%)^(b) (%)^(c) 1 0.13 Vydac ®0.275 95.3 2-4 2 0.13 Jupiter ® 3.63 96.6  6 3 0.1 Daisogel ® 4.65 99.211 4 0.1 Daisogel ® 4.72 99.0 11 ^(a)Powder weight ^(b)Analysis byRP-HPLC: Zorbax 300SB C18 (3.5μ, 3 × 150 mm, Agilent), A: acetonitrile +0.1% TFA, B: H₂O + 0.1% TFA, 15-53% A (40 min). ^(c)The yield includesall the synthetic steps from Fmoc-β-Ala-resin and was calculated on thenet peptide content of the final product. Vydac ® C18, 300 Å, 10-15 μm(Grace), ref 218MSB1015 or 218TPB1015 or 238TPB1015 Jupiter ® C18, 300Å, 10 μm (Phenomenex), ref 04G-4055 Daisogel ® C18, 300 Å, 10 μm(Daiso), ref SP-300-10-ODS-RPS

These results demonstrate that both the yields of the process ofpreparation of the conjugates according to the invention, and the purityof the obtained conjugates can be highly improved by reducing thesubstitution ratio of the resin and/or by using an appropriatestationary phase.

REFERENCES

-   1. Kaiser, E., R. L. Colescott, C. D. Bossinger, and P. I. Cook,    Anal Biochem (1970). 34: 595-8.-   2. Maemura, M., A. Ohgaki, Y. Nakahara, H. Hojo, and Y. Nakahara,    Bioscience Biotechnology and Biochemistry (2005). 69: 1575-1583.-   3. Tam, J. P., W. F. Heath, and R. B. Merrifield, J Am Chem Soc    (1986). 108: 5242-5251.-   4. Tanaka, E., Y. Nakahara, Y. Kuroda, Y. Takano, N. Kojima, H.    Hojo, and Y. Nakahara, Bioscience Biotechnology and Biochemistry    (2006). 70: 2515-2522.-   5. Bay, S., R. Lo-Man, E. Osinaga, H. Nakada, C. Leclerc, and D.    Cantacuzène, J. Peptide Res. (1997). 49: 620-625;-   6. Fmoc solid phase peptide synthesis, A practical approach, Edited    by W. C. Chan and P. D. White, Oxford University Press.-   7. Sander, J. and H. Waldmann, Chem Eur J (2000). 6: 1564-1577.-   8. Lo-Man, R., S. Vichier-Guerre, S. Bay, E. Dériaud, D.    Cantacuzène, and C. Leclerc, J. Immunol. (2001). 166: 2849-2854.-   9. Lo-Man, R., S. Vichier-Guerre, R. Perraut, E. Dériaud, V.    Huteau, L. BenMohamed, O. M. Diop, P. O. Livingston, S. Bay, and C.    Leclerc, Cancer Res (2004). 64: 4987-4994-   10. Babino, A., D. Tello, A. Rojas, S. Bay, E. Osinaga, and P. M.    Alzari, FEBS Lett. (2003). 536: 106-110.-   11. WO9843677—Multiple antigen glycopeptide carbohydrate, vaccine    comprising the same and use thereof

1. A method for preparing a carbohydrate T cell epitope conjugate of formula (I): M(T-B)_(n)  (I) wherein: M is a dendrimerie poly-Lysine core; T is a T cell epitope; B is a carbohydrate B cell epitope comprising at least one carbohydrate residue (b); n is an integer and represents the number of -T-B groups covalently bonded to M; Said method comprising the steps of: i) coupling a protected carbohydrate B cell epitope (B_(Pr)) which hydroxyl groups of the carbohydrate residue (b) are protected with a protecting group (Pr), with a compound M(T)_(n) thereby forming a carbohydrate T cell epitope conjugate M(T-B_(Pr))_(n), said protecting group (Pr) being selected from the group consisting of allyl, p-methoxybenzyl (PMB), t-butyldimethylsilyl (TBDMS), benzyloxymethyl (BOM), levulinyl (Lev), benzoyl (Bz), 2,5-difluorobenzoyl, chloroacetyl, benzyl (Bn) or an acetyl (Ac), or forming with two hydroxyl groups to which it is attached a C₅-C₆ isopropylidene ketal or a C₅-C₆ cyclic alkylcarbonate; and ii) removing the protecting groups Pr from the obtained conjugate M(T-B_(Pr))_(n) thereby obtaining the carbohydrate T cell epitope conjugate M(T-B)_(n).
 2. The method of claim 1, wherein M(T-B)_(n) is selected from the following formulae (Ia) or (Ib):

Wherein K is a lysine residue, and T and B are as defined in claim
 1. 3. The method of claim 1, wherein M is (K)₂K-βAla-OH of formula:


4. The method of claim 1, wherein T is a T cell epitope comprising a peptide.
 5. The method of claim 4, wherein T is or comprises a CD8⁺ or a CD4⁺ T cell epitope.
 6. The method of claim 5, wherein T is or comprises a CD4⁺ T cell epitope.
 7. The method of claim 6, wherein T is or comprises a poliovirus (PV) fragment protein, a tetanus toxin fragment or a PADRE peptide.
 8. The method of claim 7, wherein T is a peptide consisting of QYIKANSKFIGITEL (SEQ ID NO: 1).
 9. The method of claim 1, wherein the carbohydrate residue (b) is attached to an amino acid, peptide or lipid residue.
 10. The method of claim 1, wherein B is or comprises a carbohydrate residue selected from the group consisting of: α-GalNAc-Ser, α-GalNAc-Thr, β-GalNAc-Ser, β-GalNAc-Thr, β-Gal-(1-3)-α-GalNAc-Ser, β-Gal-(1-3)-α-GalNAc-Thr, (α-GalNAc-Ser/Thr)₂, (α-GalNAc-Ser/Thr)₃, and (α-GalNAc-Ser/Thr)₆,
 11. The method of claim 10, wherein B is or comprises the residue (α-GalNAc-Ser/Thr)3.
 12. The method of claim 1, wherein the protecting group Pr is benzyl (Bn) or acetyl (Ac).
 13. The method of claim 1, wherein step i) comprises the steps of: a) coupling a first protected carbohydrate residue (b_(Pr)) which hydroxyl groups are protected with a protecting group (Pr) as defined in any of the preceding claims with a compound M(T)_(n) thereby forming a carbohydrate T cell epitope conjugate M(T-b_(Pr))_(n); and b) repeating step a) with further protected carbohydrate residues (b_(Pr)) up to obtaining a protected carbohydrate conjugate of formula (II) M(T-B_(Pr))_(n)
 14. The method of claim 1, wherein Pr is benzyl.
 15. The method of claim 14, wherein benzyl groups are removed in the presence of TfOH or H₂.
 16. The method of claim 1, wherein Pr is acetyl.
 17. The method of claim 16, wherein acetyl groups are removed in the presence of hydrazine or MeONa.
 18. A carbohydrate T cell epitope conjugate of formula (II): M(T-B_(Pr))_(n),  (II) wherein M is a dendrimeric poly-Lysine core; T is a T cell epitope; B_(Pr), is a protected carbohydrate B cell epitope comprising at least one carbohydrate residue (b) which hydroxyl groups are protected by a Pr group as defined in claim 1; and n is an integer and represents the number of -T-B groups covalently bonded to M.
 19. The carbohydrate T cell epitope conjugate of claim 18, wherein T is or comprises a peptide.
 20. The carbohydrate T cell epitope conjugate of claim 18, wherein Pr is benzyl (Bn) or acetyl (Ac).
 21. The carbohydrate T cell epitope conjugate of claim 18, wherein B_(Pr), is a protected (α-GalNAc-Ser/Thr)₃.
 22. The carbohydrate T cell epitope conjugate of claim 18, wherein M is HO-βAla-K(K)₂.
 23. The carbohydrate T cell epitope conjugate of claim 18, wherein T is QYIKANSKFIGITEL (SEQ ID NO:1).
 24. A use of a carbohydrate T cell epitope conjugate M(T-B_(Pr)), of claim 18 for preparing a carbohydrate peptide conjugate M(T-B)_(n) as defined in claim
 1. 